The purpose of this study is to clarify the effect of the monamine oxidase inhibitor (MAOI) phenelzine, on cardiac conduction. The increasing use of the MAOI's in older patients with possible pre-existing cardiac conduction defects, make this relevant. This will be studied by performing high resolution, high speed electrocardiograms on each of 60 patients before and during a drug treatment schedule. Twenty patients will be assigned randomly to placebo, 20 to imipramine, and 20 to phenelzine. Plasma levels of phenelzine and imipramine will be measured at the time of the second electrocardiogram. Cardiograms will be read blind by an experienced cardiologist and changes in conduction assessed by the measurement of ECG intervals. Specifically the PR, QRS, QT(c) intervals will be examined and contrasted between groups of phenelzine, imipramine and placebo. Another goal will be to collect systematic data on the relative degress of orthostatic hypotension caused by phenelzine and imipramine. If phenelzine's effect on conduction is less than that of imipramine, it may be more confidently used in older patients or patients with pre-existing abnormalities of cardiac conduction.